1. Field of the Invention
The present invention relates to an organic EL panel and a filter thereof, and more particularly to an organic EL panel and filter thereof which enable the achievement of a clear, sharp image.
2. Related Art
An organic EL element is formed by an organic solid-state luminescent layer made of a phosphor such as anthracene and a positive hole-injection layer made of a triphenylamine dielectric, or a luminescent layer and an electron-injection layer made of a perylene, or a positive hole-injection layer, a luminescent layer and an electron-injection layer sandwiched between two electrodes, which is generally formed on a substrate.
In an organic EL element such as noted above, light is emitted when electrons that are injected from a cathode into the luminescent layer recombine with positive holes that are injected from an anode into the luminescent layer. For this reason, an organic EL element can be driven with a low voltage such as 4 V by making the luminescent layer thin, and also has the advantage of fast response. Because it emits light itself, it also has an advantage of a wide viewing angle.
However, the above-mentioned two electrodes made of the metal thin films have a high reflectivity with respect to visible light, and regardless of whether or not the organic EL element is emitting light, reflected light of external light striking them exits from the light-extraction surface. For this reason, the contrast of an organic EL panel in the past was relatively low.
Given the above, a filter for transmission-type LCDs is disposed on the outside of the light-extraction surface.
FIG. 4 shows a filter of the past. This filter (for example, the Nitto Denko type NPF-F1228DU) is formed by a polarizing layer 4 having a polarization of approximately 95% and a quarter-wave layer (xcex/4 plate) 23. However, an organic EL display is characterized in self-emission of light, so that it does not require as much polarization as an LCD.
In the Japanese Patent No. 2,761,453, there is indicated technology in which, for fabricating an organic EL element in which the transmittance of an electrode positioned on the light-extracting surface is 10% or greater over the wavelength region from 400 to 600 nm, and the reflectivity of the electrode positioned on the opposite side from the light-extracting surface is 50% or greater over the wavelength region from 400 to 600 nm, a polarizing film is combined with a retardation layer or film (xcex/4 plate) and disposed on the light-extracting surface. Although the cited invention causes some improvement in the contrast, it does not yet achieve a satisfactory level.
The Japanese Unexamined Patent Publication (KOKAI) No. 10-508979 (International Publication Number WO 97/07654 Al) discloses an EL panel, however this EL panel is different from the present invention in terms of problem to be solved and constitution.
Accordingly, an object of the present invention is to improve on the above-noted problem with the prior art, and to obtain an organic EL panel having a clear and sharp image, by specifying the polarization and haze value of the filter.
In order to achieve the above-noted object, the present invention has the following basic technical constitution.
Specifically, a first aspect of the present invention is a filter for an organic EL panel formed by a xcex/4 plate, a polarizing layer and an anti-glare layer, wherein the polarization of the polarizing layer is between 50% and 70%.
In a second aspect of the present invention, the haze value of the anti-glare layer is between 5% and 15%.
In a third aspect of the present invention, the xcex/4 plate layer is laminated onto a glass substrate of the organic EL panel, and onto the xcex/4 plate layer is laminated on the polarizing layer.
In a fourth aspect of the present invention, the polarizing layer is laminated onto the glass substrate of the organic EL glass, and onto the polarizing layer is laminated the xcex/4 plate layer.